This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A Virtually Imaged Phased Array (VIPA) is a modified Fabry-Perot etalon which achieves spectral angular dispersion via multiple beam interference. It consists of a fused silica plate with the back side coated with partially reflective film and the front side covered with nearly 100% reflective coating, and a narrow anti-reflection coated window. When an incident light enters the window at a certain angle, it undergoes many reflections within the VIPA to create multiple virtual images, which interfere to produce high spectral angular dispersions. The high spectral resolution achieved in such a manner allows the observation of very narrow spectral shifts by opto-acoustic interactions within the sample.